Oracle-L: RE: Analyzing indexes

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Tue, 11 Mar 2003 12:14:28 -0800
Message-ID: <F001.00566BCD.20030311121428@fatcity.com>

Chuck

I think Jared has some excellent advice (as usual). Interestingly, while you may need to lock the table while analyzing the table, you may be able to rebuild it without locking it. According to the Oracle Education notes, "Oracle8i introduced a method of re-creating and existing index while allowing concurrent operations on the base table." The syntax is

ALTER INDEX xxx REBUILD ONLINE;
or

ALTER INDEX xxx COALESCE;
If you really feel you must do something, the coalesce may be a lower-risk solution. It won't lower the height, but as Jared points out, that may be of only temporary value. Either way, I'd try it in test first.

Dennis Williams
DBA, 40%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Tuesday, March 11, 2003 1:04 PM
To: Multiple recipients of list ORACLE-L

Chuck,

I've been convinced that rebuilding indexes is a waste of time.

In fact, it can cost you time, as rebuilding indexes can kill your peformance while the indexes again seek their 'level'.

Check into at asktom.oracle.com. There's some good examples.

jared

"Chuck Hamilton" <chuckh_at_softhome.net>
Sent by: root_at_fatcity.com
03/11/2003 06:30 AM
Please respond to ORACLE-L

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        Analyzing indexes

I need to determine whether or not a couple of indexes need to be rebuilt. The problem is the indexes are quite large and on a 24x7 high volume database. If I try to run an "analyze validate structure" to gather the data
I need to make that decision, it sets a lock on the table for about an hour
which I can't afford to do. There is no slow time when I can do this and management has said before they're not going to spring for the partitioning
option to break the indexes up into managable pieces. Is there some other way I can get the information needed to determine if an index needs to be rebuilt or not without setting a lock on the table? We are on Oracle 8.1.7.

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Author: Chuck Hamilton
INET: chuckh_at_softhome.net

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Author:
INET: Jared.Still_at_radisys.com

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